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DIAPHRAGM EFFECTIVENESS IN PRESTRESSED-CONCRETE GIRDER BRIDGES

Overheight vehicles and vehicles carrying overheight loads damage many prestressed-concrete (P/C) girder bridges each year. Researchers studied the effects of this type of loading on P/C bridge behavior for various types and locations of intermediate diaphragms. The study included a comprehensive literature review; a survey of design agencies; the testing of a full-scale, simple-span, P/C girder-bridge model with eight intermediate diaphragm configurations, as well as one model without diaphragms; and the finite-element analyses of the bridge model assuming both pinned- and fixed-end conditions. Investigators determined that vertical load distribution was independent of the type and location of the intermediate diaphragms, while the horizontal load distribution was a function of the intermediate diaphragm type and location. Construction details at the girder supports provided significant rotational-end restraint for both vertical and horizontal loading. Girder-end restraint affected both vertical and horizontal load distributions. A fabricated intermediate structural steel diaphragm fared as well as the reinforced-concrete intermediate diaphragms in terms of response to lateral and vertical loads.